The chemistry and assembly of ciliary, flagellar, and cytoplasmic microtubules is being investigated in order to elucidate their function in motile processes. Tubulin dimers from A, B, and central pair tubules of sea urchin and molluscan cilia and flagella have been resolved electro-phoretically into their respective subunits and these are being compared with respect to differences in amino acid composition and tryptic peptide maps. How related are these chains and can their primary sequence characteristics be related to their distinct association properties in the cell? Cytoplasmic tubulin polymerized in vitro is being investigated in regard to the role of associated proteins or nucleotides in the control of polymerization. High hydrostatic pressure or low temperature are being used as probes to perturb this equilibrium system. The control of tubule polymerization in vivo will be studied using ultraviolet microbeam techniques for selective inactivation and lysis or microinjection techniques for reactivation. The assembly of sea urchin embryonic cilia is being investigated with regard to the synthesis and control of linkage and spoke proteins of the 9 plus 2 structure and also the differential synthesis of specific tubulin subunits. Bibliographic references: Stephens, R.E., "The Basal Apparatus: Mass Isolation from the Molluscan Ciliated Gill Epithelium and a Preliminary Characterization of Striated Rootlets," J. Cell Biol. 64: 408-420, 1975; Stephens, R.E., "High-Resolution Preparative SDS- Polyacrylamide Gel Electrophoresis: Fluorescent Visualization and Electrophoretic Elution-Concentration of Protein Bands," Anal. Biochem. 65: 369-379, 1975.